Automatic telephone system



Patented Dec. 7, 1926..

CLARENCE E. LOMAX, OF OAK PAB/EL, LLENOIS, ASSIGNOR,`BY MESITE ASSIGNMENTS, TO AUTOMATIC ELECTRIC INC., OF CHICAGO, 'ILLINOS, A. CORPORATION 0F DELA- WARE.

, Au'roivraric rnnnrnoian s Ys'rnr/i.

`Application filed lApril 15. 1921, Serial No. 46715575. Renewed April 26, 1926.

i The present invention relates in general to automatic telephone systems, but more especially to small systems such as are commonly known as private automatic exchanges; and the object of the invention is to provide animproved form of connector switch for use in a systemV of' this kind. More specifically, a connector is provided which is of the monitor type, that is, it may be used for supervising or monitoring busy lines and trunk lines, althoughitfis used also by the otlicialor other person to whom it is assigned tor establishing all ordinary connections. l g y The Ainvention may beV better understood from abrief description of aprivate automatic exchange system in which it isA adapted to Vbe used. A system of this kind usually has a capacity of less than 100 lines and the subscribers lines are. ordinarily provided with individual line switches which have access to a plurality of Vconnector switches which are used for establishing local connections and also trunk connections to the main exchange. l/Vhen a calling subscriber removes his receiver his individual line switchl is operated automatically and connects his line -to an idle local connector switch, which responds to successive actuations of the calling device dial at the calling station to complete the connection to the desired local station, assuming that a local call is being made. To handle trunk connections a group of trunk lines connecting'with the main exchange may be terminated in the local connectors, usually in the tent-h level. In making a call to the main exchange, the calling subscriber will operate his calling device in accordance with the digit O and when the local connector in use is raised to thisv level it operates automatically, somewhat in the manner o'l a selector switch, .and establishes connection with the first idle trunk line encountered. Y

Now, in a private automatic exchange of the, kind described established connections are entirely secret, because no 'operators vare involved in theconnectio'ns in' any way, and this is a very desirable feature in that it prevents operators, or other unauthorized persons, from listening to or otherwise in-` terfering'with established connections. A

possible disadvantage, however, arises from sonal subjects entirely unconnected with the business. Thepresent invention renders it possible to detect such improper practice and at the same time it affords an oiicial, or'other person having supervisory authority, a convenient method of exercising general supervision over telephone traiiic;

In its physical embodiment the-invention comprises a special connector switch, which may be termed an otlicial connector, or a monitor switch. This connectoris not intended torcommon use like the'local connectors, but on the contrary is individual to the line lot the. oiliciah'or other person to whom it is assigned. It is used for' establishing all ordinary local and trunk connections, and in addition has special circuitarrangements for performing the various monitoring or supervising functions which are necessary. These functions include the monitoring of busy local lines, and also the monitoring of busy trunk lines. The circuit arrangements are such that thereV is no interference with automatic calling or with talking on lines kwhich are being watched, and the parties using such lines are not necessarily appris-ed of the fact that their conversations are being listened to;

A. further feature or modification may be used to advantage where an entire level is available as, for example, in a case where there are perhaps-80 or less local lines and 10 or less trunk lines to the main exchange, there being at least one level left which is not in use at the local connectors.k This level may be Vused in the official connect-oi"v andadords a very easy way'of monitoring calls where it is not necessary to know vwhat particular lines aretalking. p The procedure is to multiple the trunk lines incoming to the local connectors in the particular level to be used for this purpose in the orflicial connector (usually the ninth level), and since there are. only a' relatively small numF ber ot connector switches, the person who is monitoring the calls can obtain access to all established connections veryl easily.

l Referring now to the drawingA in which Who' is k'authorized to .supervise 'the telephone.` tr'alric.v The line conductors '11'nand112 dof..`

not terminate in an individual line switch as is the usual practice,

.\ to the specialconnector H, which isA the otHcia-l connector,Y or"`m`onitor"svv'itch` 'previously referred to. l-This connector is a v ertical" andfrotaryd switfch of" the A`u`sfu-al 'Strovv ger ',-type and vis'.operated according" to, the Well'knovvn twoftvires'ystem of control. ffOf the .ten levels of banlrucon'tact'sets'inthe monitoru switch .only the i' lifrst contact? sets inifthe eighth, ninth. and. te nth'l'ev'elsv vfare shown l in the 'drawing The A`iirstl .eight i levels are "as'sun'` ed .-tol bef "reservedfor the lo'calilines'. iny the. exchange one yo f'l'-3lie`se lines,4 theiline,v 'extending to V the' automatic substation A", is terminated Vin fthe lirst contactA set in f the. yeighth ,l'evelL/'shovynjlinf the dravving. 'lfhe'niiith leve-1 islutilizedftogive thejmoni't-or swit'chv 'accessv ftothe" -loal "com riectors for. .p'urposesi previously explained,

andeontains a multiple' of ea'chfot the trunk lines extending' toy such. local connectors, f one U of thesetrunk vlines,"fthe one.' Which'te'rminates in ltheflirst contact? set in the" 9th vlevel being .shovvnl in`ithe drawing. The t''litli level is. used.. fof'tiiunk Ylines vto themain' exchange and `one 'Itliese'trunklines isalso .terminated vin theffrstconv'lt Will'v .be undert'act set. in vthefte'ntli level. stood` that all 'of .the l levels :ofthe monitor are; con-nectedv` 'in` ,iiiul'tiple .Withgthe ,corresponding Ylevels .of f' the nlocalI1 connectors. l`he reference)character C indiea'tesl a' line svvitch which. 's f individualfto. the?" -line eX tending to: fth'ef ,z t'utoinatic1fy substationv A. This linefs'witch ofthe ivellliioivn rotary typelin ivliiehthe Wipershavenolnormal posit-ion"and move`in a 4torvv'ard direction only. i i .I

'lflie operation. of the system will' nowf` be explained, ,it ,being assumed for thisA purpose thatmthebtlieial the telephone substation A :fdesirfes. to establish'Y connection ivithtlie subscriber at*A the local substation lAf LWhen the receiver'isremoved a circuit is-c'oi'npletfed ov'er the line conductors 1l and l2" ft',or4 Vfthe doujleivundline relay 2 3 in the connector Uponfenergizing,lrelay[23'closes a circuitvv fort-he slow: acting'release relay 24. Upon f energizing.,k in lturn, the? latter relay sivitclnavitli the Venception -ofthe ninth level,

i preparesacircuit torfthe verticalY magnet 30 i'lhe calling -d'eyicewat substationilAniay but eXtendfdiretly?" working contact, oi normal springs 33 and 35, Windings'of'the sl'ovvacting series relay 25, and the Windingof the vertical magnet 30 to battery. lBythe 'operation o the vertical ina-"gnet,l th.e"s li'a tt1ot the 'svvit'cli'l'is raised step' 'by step miur the wipers 80,1 8 1, 'and 82 are brought torestfop'positef the'l'desiredhorizontal level ofbank contacts, which inI this case "the eighth level. The 'slow acting relay: 25 is energi'zediir seriesiviththe vertical magnet, ture '58 attracted g throughout fthe "vertical operation "oi' the switch 'maintains' the vertical magnet circuit; intact after heeft normal', springs have been shifted', ivhifch Voccurs on' the li'rst vertical 'movement of l the"switch shaft. `At theend Aofthe verticalpp'eration otfthef` switch, relayl 25"'re'tracts 'its armature and transfersthe' operating Y circuitV to the 'rotary'magnet I31.

The calling-' device "at substation" A j may novvbe operated in yaccordance with the sec 0nd :digit in the desired number, "and as" before a seri`eso f 'interrufptions y is 'produced in 'the 'circuit of the line relay i, 23. *This time, g up on AdeenefrgiZii'ig in respoi'ise tothe interruptions in 'j its "circui t', the 'line relay sendsg impulses 4to Athe rotary ma'g'net "31 over the following circuiti Fromgrouiidl'jby ivay' of varmat'ure '45V and lits resting: Contact, aventure ,4T its*working".coitt formalspringsV 33"a1fidA 34, armature fand its resting ntactjresting contactfof vtarma.- ture Glvand ythe visa i c l` armature, V Winding of' 'the' 'slow "actlngj's'eries relay Y 2 7 :and the 'wvii'iding offrotary .magnet 31 to 'batt'ery. By' the operation of the rotary" niagnet, the Wipers 80, "8` l,";a nd f8 2 are 'rotate-d step by step and I are jfinally` brought Vto rest in engagement "With the particular setI fof bank contacts .inwhich the desired called line lis" terminated. ,In the 1 present "case, sincethe' y called line is the line of substation A', ivliieh'fisf terminated in" the lirst set 'fof bank contactsv in{`t l' 1e'e igl1tli leveLthe switch Wipers Will 'be rotated?onlyffonestep Aand'y vvill be brought to rest injengagem'ent with bank contacts k83, lgandf. 8 5. The slow acting series relay 27 is'ene'rg-ized-4 in ser'ies with the iQtary "magnetf31' andreni'ains in operated position" throughout the rotary movenient of theswitclr At its armature "54, y 1e lt ry 2"r' connectsffthetest Wiper'l tothe Winding 'of the test 'relay 28,? wliileatv armaturef'-the connection'between'the two lright yhand y'vi/indings of tlierepeating coil, which are' nor- 30, and/byu holding' its@ armallf:

over again after a brief interval, or

mally bridged across the line wipers 80 and rotary movement ofthe switch has been completed, a locking circuit is completed for relay 28 at armature 56, while at armature 57 the circuit of the upper winding ofthe switching relay 29 is opened to prevent this i relay from pulling up. Relay 27 having deenergized, and the line wipers being ink engagement with the bank contacts in which the called line is terminated, a talking or listening circuit is completed in an obvious manner, and the oiiicial at substation A willk be able to listen to the conversation which is taking place between the party at substation A and whoever it -is that he is talking to. If the oiiicial desires to listen to the I: conversation for a few minutes to determine its character he may operate. the transmitter ter cut-out button P at his telephone in order to render his own transmitter inactive. It will be observed that the connection as now 1 established includes the windings of the re repeating coil, and it will be observed further that the battery feed relay 22, which ordinarily supplies talking current to the called subscribers line, has not been connected up because of the rfact that lthe ring" cutoff relay 26 has not been energized. 'lVitli these circuit arrangements the oiiicial can listen in on the called line to good advantage, whiley at the same time he does not, in any way, interfere with the conversation that is going on and if the transmitter cutout button is depressed, the establishment of the connection will ordinarily be effected without attaracting the attention of the parties who are talking.

Two courses are now open to the calling party, assuming that he actually wishes to talk to the party at substation A. l He may hang up the receiver and call the number he may wait on the line until it becomes idle. Assuming that the latter course is'followed, when the calied line becomes idle the ground potential is removed from the test contact 8st and the test relay 28 will deenergize, thus closing a circuit for the switching relay 29 which extends fro-m the grounded private normal conductor 14 by way of the resting contact of armature 57 and the said armature, the upper winding of switching relay 29, resting Contact of armature 54 land the said armature, test wiper 81, test contact 84L private normal conductor 102, winding of the switching relay 104 of the line switch `C and the winding of the stepping magnet 106 tobattery. Upon the closure of the above circuit, relays29 and 104 are energized in series, and the latter relay clears the line of substation A of its normal battery and ground connections in the line switch C. It may be explained that at the present time, due to an interlocking` device controlled by the line relay 105, relay v104 is energized only about halfway, and the wipers' of the line switch are not connected up.

lAt the connector H,`when thev switching relay 29 is energized it establishes a locking circuit for itself at its armature 60, opens the rotary magnetcircuit at armature 61, and at armatures 5 8 and 62 completes a signalling circuit for operating the ringer at substation A. Ringing current from ,the generator GEN is now projected out over thel called line in the usual manner to aty tract the attention of the' subscriber at substation A. The upper winding of the ring cut-ofi relay 26 is included in the circuit and when the called subscriber answers by removing his receiver from the hook relay 26 is energized, establishing a locking circuit for itself at armaturel. In addition, relay 26 breaks the ringing circuit at armatures 49and 53, closes a point in thetalking circuit at the latter armature, andat armatures 50 and 52 connects up the battery feed relay 22 for supplying talkingv current; to the transmitter at the called'station. The complete talking circuit has now been established and the two connected parties can converse as desired. Q

`When the conversation is nished both the parties will hang up their receivers and the connector H .is restored tonormal by the replacement of the receiver at substation A. This operation opens the circuit of the line relay 28 and relays 23 and 24 are accordcompleted for the release magnet 32. By the operation of the release magnet the yconnector switch is restored to Ynormalposition in the usual and well known manner. Ground is alsoremoved from the private normal conductor la, which unlocksrelays 26 and 29, and at the same time removes the busy condition from the line of substation A and rendersit accessible to incoming calls..

` It will be assumed now that the otiicial at substation A desires to obtain a' connection with someone in the mainl exchange. The operations which take place are substantially the same as those which have just been described, except that the calling device is stated further that when the switch shaft is ingly deenergized, whereupon a circuit is raised to? the tenth'level'the cup spring 'casingat' the'top 'of the shaft engages'with contact 'spring faiid causes" it'toeng'age with contact! spring 36, thus' closing an energizing circuit or'relay `21..t Uponenergizing,` relay 21' disconnectsthl'e battery feed relay'22 and prepares a loop repeating circuitiwhich' will loe `described presently. i Relay' '2l also closes acircuit for the'iing cut-oft Yrelayv 26 which is energized and locked `up* for the purpose of opening ther ringingfci'rcuit, 'as it 'is' not necessary to=ring out overthe tru'nlcline to the -niain exchange. i

To ycontinue with the v`operation' of the connector H, and` assuming .that the wipers haVe-beeniraised and rotated-into engagement with'theliirst set'of contacts inthe tenth "levelyii'f the firstl trunlline is busy the test-frelay'28 will be yenergized just as was described -in' the previous Caseland switching relay 29 vwillfbe prevented from operating. The saine listening circuit is completed; howeverywhen the' slow acting relay 27 falls back at. the-end'foi the frotaryni'ovenient' of* the switch and the party at? substation will be able'to tell what is talking place on tlietrunlz line. Vl-:leinay listen to the 'conversation that is going 'onii he'considers'it"necessary, 'oriii he desires to complete his own connection he will proceed to` "test the other trunk lines =in order to 'obtain an idleone whic'hniay' be used to set up theldesiredconnection. f This testingI is. accomplishedby 'calling the"I digit lrepeatedly until' an idle `trunk is located. When the digiti is called,th linee relay" 23 operates tov trans'niitano'ther iinp'ulseo'i current to' the 'rotary magnet 3land the switch wipers are advancedv another step in order to connect withv the "second t'runki line ofthe group. if this 'tru'nl lineis lbusy'alsogthe party'at'subst'ation A will "c'all'fthev digit l againy and so lonu'ntil a trunk line` is i'und which'is idle. idle trunk line, the test wiper Sl'will lindlno ground potential onfthe bank lcontact which itfengages andthe test relay 28 will" fall back and'close the' u'sual'energizing'circuit for the switching' relay 29. For vthe 'purpose of describing the' 'operations "resulting` from the'energi'zation ofthe vlatter YrelayY 1t in'ay be assumed that the irst trunk" 'line, 'or Jthe line which terminates in bank contacts 89,

v90 and V91,'was found to be'idle whenfconnectionlwas attemptedtherewith. Under' these ci'rcunistances,` switching 'relay Y29 is v"enen gi'zedat'once as soon as' the" slow acting relay 2T falls Vback' and perf'iorinsits usual 'iunction', except that inthis'case no'iinging circuit' is-'coinpleted due tothe fact; that the ring cut-off relay 26 has already been'ener- "giz'ed V"ln addition a bridge, referred'io hereinbeiore as a loop repeatingcircuit7 is closed across the trunkconclu'ctorsA 92 and 94 as follows:,from the lconductor 92 by vway of bank contact`89, wiper' 8O,4 upper rightwoef/iso hand winding ofthe:'iiepeatingicoil; working contact 'oi'f-armature'l iand "the `said 'farinature, varrnatiires' 42f -rand :its )working contact, ariiiature 59 and its-working contact, armature 44S and its working contact, lower" righthandiwiding. ofjthe repeating coil, working Contact of yarniat'u-re 53 and the v said'l arma tu're, working y"c'on'tact'foi Iarmature 62 and the said ialrinatureywiper-825`and bank contact'l91 to theftrunk line conductor 194. .At the inainex'changelthe Vtrunk lineconductors 92. and 94 may i terminate lin the* linev relay of an Lincoining selector switch,I and-by `the closure cithe biidge j ust fdescribed. the line relay loi'r ythis selector switch 'is operated; Uponv energizing, the: line V`'relay closes afcircuit ier the k"associated slow vacting "release relay Land "the, select-or is IVprepared for roperation 'in the usualiiianner.

The callingdevi'ceidi'al' at substationfA inay now? be 'foperat'edwin accordance i with the digitsfin the number/oi the party wanted at the ina'in' exchangegfand `as a result a plu-rality of.l series' 'foi' interruptions is produced in the 1 circuit of the line relay'l 23,",which Iare re* peated at arniature 44k Foi r'thefsaidf line relay into' the Abridge acrossl the ltrunk conductors 92 and "94, causing-the vincomingselector yat theh distantmain "exchange 'and' aplurality of other switches' to be :operated to complete the desired connection tof'the 'called' line. lhese'fop'erations "aref well understood `land since the!"v invention I is' noty `'especially 'cene c'erned [with them it will be'u'nnecessaryto furthjerfarnpliyf thev explanation 'along this line. They connection is releasedthe'sanie as in thelpreceding'case where a local'con'n'ection was established.

"Although in the ior'egolng'it has'be'en' assuinedthatv the 'oilicial Vat v:subs'tation A actually wished"toestablish certa-in connections, itV will' be ymiderstood lclearly that' substantially 'the's'aine opeiations'are goneth'rough with incase itfisi desired 'inerely' tov monitor or supervise certain lo"c'al",lines,v `or -trunlr lines. inthe case foi' a ',{trunl line to' 'the niainfeXchangeQ-the party V'canflisten'in lon all oi the Vtrunlrs within a "short time 'by calling the nuinher corresponding tothe iirst "trunk, iii'hicli isthe Inuiiiloe1 'U?,V vand thengfollowing up byfcallifngthe digit fatiiiter'yals until au 'idle trunleline is reached. It allA oi' the trunk lines 'f are busy it will he 4clear v"that they will'all 'be connected withy s ticces'rsiyely, thus vperinitting the otiicialggorfother person who is inonitoring'the calls, to'hnd out'what is going-enjeu each trunk line. 'Itan idle trunk line" shoulldf'fbe J'encounteredf'before all of the trunklineshaye"beentested in this way the "switching" relay V.29v will loe energized and 'it' will befnece'ssary toha'ng upithereceiver and release' the'conn'ector switch, after which it is ige-operated inacc'or'dance with the number of'tlie'nezit trunlrvline'siioceed- Ving the line. which was found to'be idle.

llG

The operation of monitoring calls by cutting in on the trunk lines leading to the local connectors will now be' explained briefly. As pointed out before, these trunk lines are inultipled in the ninth level of the monitor switch, shown particularly in the case of the trunk line comprising conductors 110 to 112, inclusive, the line conductors of which are connected by means of conductors 108 and 109 with bank contacts 86 and 88,]which bank contacts together.

with bank contact 87 comprise the iirst set of contacts .in the ninth level. The operation of connecting with these trunk lines vfor monitoring purposes is precisely the same as was described in the case of monitoring the service on the outgoing trunk lines to the main exchange, with one exception however. Since all of` the test contacts on the ninth level, such as the test contact 87, are left dead, the switching relay 29 cannotfbe energized, no matter whether the trunk line connected with is busy' or idle; andv it follows, therefore, that all of the localtrunk lines may be tested or monitored by calling the number 91, which causes the monitor switch to connect with the first trunk line, and by following this up by calling the digit l at intervals in order to transfer the connection to all of the other trunk lines in succession. Since the switching relay 29 can never be energize-d during these operations, it follows that all of the local trunk .lilies and consequently all of the established connections in the private automatic exchange, whether local or trunk, can be listened in on within a very short space of time.

Before `closing it maybe pointed out brieiy what takes place when the line of substation A is called. When one of the local connectors is'operated by some other subscriber to connect with the line of substation A, the connection is established by way of the normal conductors 13, 14, and 15, and ground potential is placed on the private normal conductor 14 through the vswitching relay of the local connector which is in use; lAs a result, the cut-olir1 relay 20 is energized to disconnect the line conductors 11 and 12 from the left-hand windings of the repeating coil, and to connect them instead with the normal conductors land 15'. There is nothing especially new in these operations, however, and it'will be unnecessary to consider them further.

Having described my invention, what I consider to be new and desire to have protectd by Letters Patent will inthe appended claims.

What I claim as my invention is; 1. In an automatic exchange, a monitor switch accessible to a telephone line, means whereby the subscriber on said line can op Vbe pointed out .crate said switch te establish ccnnecton with comes idle,

lish other circuits for listening cuit between said lines when the called subv-l scriber answers, a battery feed coil, and,

means for connect-ing said coil to the talking circuit in the second case but not in the first.

2. In an automatic exchange, a monitor switch accessible to a telephone line, means whereby the subscriber on said line can 0pcrate said switch to establish connection with anothery subscribers line, means for locking said switch on the called line in case the same is busy, means for establishing an inductive listening circuit to enable the calling party to hear the conversation onthe called line, and means for automatically signalling the `called subscriber when the called line becomes idle.

3. In an automatic exchange, a monitor switch accessible to a telephone line,y means 'whereby the subscriber on said line can operate said switch to establish connection with another subscribers line, means for locking said switch on the called line in case the same is busy, means Vfor establishing an inductive listening circuit to enable the calling party to hear the conversation'on the called line, lmeans for automatically signalling the called subscriber when the called line beinductivewindings for feeding talking current to the called line, and means for altering the talking circuit connections to include said windings when the called subscriber answers.

4. In an automatic exchange, a monitor switch, telephone lines accessible to said switch, means for operating said switch .from another telephone line to establish a .circuit for listening on a busy called line,

and means for further operating said switch without releasing the same toestablish a circuit for listening on anotherbusy called line.`

5.A In an automatic exchange, a monitor switch, Vtelephone lines accessible to said switch, means for operating said switch from another telephone vline to establish a circuit for listening on a busy called line,

and means for causing successive further operations of said switch to successively .establish other circuits for listening on a plurality of other busy called lines.

6. In an automatic exchange, a monitor switch, telephone lines accessible to said switch, means for operatingsaid switch `from another telephone line to establish a circuit for listening on. a busy called line, means for causing successivefurther operations of said switch to successivelyestabon .a plurality of otherbusy called lines, and means for auternatically preventing further cperaticn Cil y said 'local connect J line l terminals i. in one @eating line ifsv con ofsaidzswitch in case an idle line is encountered? l v 7.l'Inf an automatic exchange, agmonitor 'switclna group of trunk lines accessible:` to 'saidfswitchfmean's whereby the partyffto 'whoiirsaid switch is assigned can loperate thev saine y"to connect with said trunk lines snccess'ively,fit being unnecessary to release the ail switch between successive yconnec- -tionsyand Ameans insaid switch for establish- ,liiies',"'" lind branchesfe'xtending' from said trunkV-A Ilines to l said hionitor switch, whereby said monitor switch isgiven access,,tofthe *s also,-'" r `'9.' In" 'an antomatic exchange, a plurality oia siibsc'rib'er's-lines,"a switch individual to "each'of saidV lines, trunk 4lines accessible to all of Said switcliesfin common and entendingto local,connector'switches which have access tonvalllof said subscribers lines,` and r 'o`f";`said individual switches comprising 4a Y'miiltilile'of :all Vthe subscribers," Aline terminals "in said' ,f local "con- IOIii-an automatic exchange, a monitor "switch 4accessible?tcfa telephQ'ne'li-ne, 'inea'ns whereby 'the siibscriber on Said *line can l operate saidw'itclito "establish connection with another suloscribers"Eline,"I a relay in saidswitchfenergiz'ed whilefthe switch is I -vand deenergize'dwhenthe ,called g Y Vnected with", a talking 'ircuit'fco'nipieten" ty'j gaia retry in @afge the eaiieci im@ isbiisy, another relafy riii sa'i'dyswitchrvnergized whenfthe lcalled' line lis vconneclrjed with isgid'le', and contacts 'on' Asaid second relay Y and "for completing af signalling circ'uitg 11.'V Inf a 'telephone Ysystem,"*acalling' line, a called line,fa 'nioiiitrl switchv ind'ividiialto Y inans rwhereby"thecalling siibscribefioper'ates aid @witchv in a ye'rtical moxi'ment :theln i rotaryjA movement to coiihectfwithfthe; ,calledfline,V af relay inis'aid switch?nrgiiedldiiring the rotary inlove f n t ment of saidj `Sw1tch ailddeener'giz'ed shortly threaltegjline Ywipersy L'andwindings of Y a nection ,normally including the rline wipers aiildl two' windings of the repeating coil in" serriesgand,coiitactson said relay for, opening sai seriesconii'ectionfat 'pointloetween the the` grotary "moyenient' fof *said "switch, said on actsalso reestablishing'saild series'con- C w,. y Vv v, H I ,v vnection*shortly after the rotaryV movement 4said;

or opening saidtallinggoircuit lines and a group wipaifggjf" nie repeating'"Coiilauifiirg scriber'- operates` Saidfswit'ch `vertical moveii'ient'landr va rotary movement Ito 'connect with thefcalledv lin'efafrela'y inx'said switch "energized during fthe'i'otary movement aiidffdeen''ergized` shortly;L thereafter, contacts jon Said 1relay *normally* included, in a f1 talking circuit `"ext'ending -tli'ronglif 'said switch, "said contacts openingtlie talking cir'- cni't cliiriiigztlie rotary" incveme'nt" oteaid .switch ,"an'd said'c'ontacts establishing'a listening circii-it Aortl'ife' calling'` l'inej'fehort'ly Y vafter the rotaryY v'movement' ,is f completed in "13; In'v a telephone TStem', acalling line,

accessible to` the call-- l 'yfthe i callii'igv subing oline, in ne wher scribjer operates sare ment and dee'nergi'aesA shortflyrl thereafter, contacts'on said jrela", li'ne"wipers' 'and fa repeating coil i'i'i'fsaidfswitcli, andl'a talking' '141i Ii'ia tele'phon'e exchange, a calling line, vcalled subscribers* linges; a' group 'of Voiitgoing tr'unirsfextenfiing t0=antiieijferehnge,'

foy) the-calling lsubscriber for operatingsaid 'lines' or fone of saidj outgoingt'runks, means for Y signalling" vthel called f 'stilosci`^iher in case a subscriber' has been called, a'repeat- ,ing coil in` said switchg'means responsive to the called subscriberfanswe'ring for connecting talkingfbaltter'over two `windings "of said? repeating 'coil in? series to the c'alled','l -iiie,

and 4'inem/gijs" f operatiye l ,responsivev -to the calling'subscriber operating'said' switch' to' the "15.'11i'a telephone exchange, 'a calling line, a switch'access'ibl V't'o said'iline', subscribers7 A 4"of outg; "ng trunks-tonnoth'er exchange terminating inly'the` banks of said switch, means whereby lines orany'o'nefof said-'outgoing trunks, a repeating icoil ins'aid switch," means for feedingl'talliiigfbattery" oyer two "windings, o

scibers linesfin'fcase they a're'called, a relay the 'called'v line,` a relay-'iin' "said switch' energiaed "during A'the' rotary movescrlber can `operate saidswitchfto connect with either a calledone of V'said subscribers in said switch adapted to be operated only when the switchis operated to connect with one of said trunks, and means controlled by said relay for cutting out the battery feed and for closing a bridge across the connected trunk including the windings of the repeating coil in series.

16. In a telephone exchange, a calling line, a switch accessible to said line, subscribers lines and a group of outgoing trunks to another exchange terminating in the banks of said switch, means whereby the calling subscriber can operate said switch to connect with either said subscribers lines or said outgoing trunks, means for feeding talking battery to the subscribers lines in case they are called, line wipers, a condenser and windings of a repeating coil in said switch, a series circuit normally including the line Wipers, the condenser and two windings of the repeating coil in series, a relay in said switch adapted to be operated only when the switch is operated to connect with any one of said outgoing trunks, and means for operating said relay in case the switch is operated to the group of outgoing trunks to cut oil the kbattery feed and to short circuit said condenser thereby closing a bridge across any one of the outgoing trunks which may have been called, said bridge including the line wipers, the short circuit around said condenser and the two windings of said repeating coil in series.

17. In a telephone system, a calling line, a connector repeater switch accessible to the calling line, subscribers lines and outgoing trunks terminating 1n the banks of said switch, means wherebythe calling subscriber vcan operate said switch to connect with eitherY said subscribers lines or said trunks, line wipers, a condenser and windings of a repeating coil in said switch, a talking circuit including saidline wipers, said condenser and two windings of said repeating coil in series established in case the switch has been operated to a busy subscribers line or a busy trunk, and means operated in case the switch is operated to an idle one of said trunks for short circuiting said condenser so as to enable the switch to repeat impulses over said talking circuit to the idle trunk.

18. In a telephone system, an automatic switch, subscribers lines and a group of outgoing trunks terminating in the banks of said switch, means whereby a calling subscriber can operate said switch to connect with either said subscribers lines 0r said outgoing trunks, three different talking circuits in said switch, the first of said talking circuits established in case a busy subscribers linehas been called, means for establishing the second of said talking circuits in case an idle subscribers line has been called, and means for establishing the third of said talking circuits in case an idle outgoing trunk has been called and the connection completed thereover.

In witness whereof, I hereunto subscribe my name this 2nd day of April, A. D. 1921.

CLARENCE E. LOMAX. 

